# state.py - fsmonitor persistent state

#

# Copyright 2013-2016 Facebook, Inc.

#

# This software may be used and distributed according to the terms of the

# GNU General Public License version 2 or any later version.

from __future__ import absolute_import

import errno

import os

import socket

import struct

from mercurial.i18n import _

from mercurial import (

    encoding,

    pathutil,

    util,

)

_version = 4

_versionformat = b">I"

class state(object):

    def __init__(self, repo):

        self._vfs = repo.vfs

        self._ui = repo.ui

        self._rootdir = pathutil.normasprefix(repo.root)

        self._lastclock = None

        self._identity = util.filestat(None)

        self.mode = self._ui.config(b'fsmonitor', b'mode')

        self.walk_on_invalidate = self._ui.configbool(

            b'fsmonitor', b'walk_on_invalidate'

        )

        self.timeout = float(self._ui.config(b'fsmonitor', b'timeout'))

    def get(self):

        try:

            file = self._vfs(b'fsmonitor.state', b'rb')

        except IOError as inst:

            self._identity = util.filestat(None)

            if inst.errno != errno.ENOENT:

                raise

            return None, None, None

        self._identity = util.filestat.fromfp(file)

        versionbytes = file.read(4)

        if len(versionbytes) < 4:

            self._ui.log(

                b'fsmonitor',

                b'fsmonitor: state file only has %d bytes, '

                b'nuking state\n' % len(versionbytes),

            )

            self.invalidate()

            return None, None, None

        try:

            diskversion = struct.unpack(_versionformat, versionbytes)[0]

            if diskversion != _version:

                # different version, nuke state and start over

                self._ui.log(

                    b'fsmonitor',

                    b'fsmonitor: version switch from %d to '

                    b'%d, nuking state\n' % (diskversion, _version),

                )

                self.invalidate()

                return None, None, None

            state = file.read().split(b'\0')

            # state = hostname\0clock\0ignorehash\0 + list of files, each

            # followed by a \0

            if len(state) < 3:

                self._ui.log(

                    b'fsmonitor',

                    b'fsmonitor: state file truncated (expected '

                    b'3 chunks, found %d), nuking state\n',

                    len(state),

                )

                self.invalidate()

                return None, None, None

            diskhostname = state[0]

            hostname = encoding.strtolocal(socket.gethostname())

            if diskhostname != hostname:

                # file got moved to a different host

                self._ui.log(

                    b'fsmonitor',

                    b'fsmonitor: stored hostname "%s" '

                    b'different from current "%s", nuking state\n'

                    % (diskhostname, hostname),

                )

                self.invalidate()

                return None, None, None

            clock = state[1]

            ignorehash = state[2]

            # discard the value after the last \0

            notefiles = state[3:-1]

        finally:

            file.close()

        return clock, ignorehash, notefiles

    def set(self, clock, ignorehash, notefiles):

        if clock is None:

            self.invalidate()

            return

        # Read the identity from the file on disk rather than from the open file

        # pointer below, because the latter is actually a brand new file.

        identity = util.filestat.frompath(self._vfs.join(b'fsmonitor.state'))

        if identity != self._identity:

            self._ui.debug(

                b'skip updating fsmonitor.state: identity mismatch\n'

            )

            return

        try:

            file = self._vfs(

                b'fsmonitor.state', b'wb', atomictemp=True, checkambig=True

            )

        except (IOError, OSError):

            self._ui.warn(_(b"warning: unable to write out fsmonitor state\n"))

            return

        with file:

            file.write(struct.pack(_versionformat, _version))

            file.write(encoding.strtolocal(socket.gethostname()) + b'\0')

            file.write(clock + b'\0')

            file.write(ignorehash + b'\0')

            if notefiles:

                file.write(b'\0'.join(notefiles))

                file.write(b'\0')

    def invalidate(self):

        try:

            os.unlink(os.path.join(self._rootdir, b'.hg', b'fsmonitor.state'))

        except OSError as inst:

            if inst.errno != errno.ENOENT:

                raise

        self._identity = util.filestat(None)

    def setlastclock(self, clock):

        self._lastclock = clock

    def getlastclock(self):

        return self._lastclock